90,266 research outputs found
Utilization of unique mare stratigraphy for determination of lunar surface material properties and location of subsurface operations facilities
Iron line profiles including emission from within the innermost stable orbit of a black hole accretion disc
Reynolds & Begelman (1997) have recently proposed a model in which the broad
and extremely redshifted iron line seen during a deep minimum of the light
curve of the Seyfert 1 galaxy MCG-6-30-15 originates from matter spiralling
into a Schwarzschild black hole, contrary to previous claims that the black
hole may be spinning rapidly (Iwasawa et al 1996; Dabrowski et al 1997). Here
we calculate in detail the X-ray spectrum produced by their model using the
full reflected continuum emission, including absorption features. This
calculation takes into account the doppler and relativistic effects. For the
range of parameters we consider, we find that the spectrum should show a large
photoelectric absorption edge of iron, which is not seen in the data. The
absorption edge is a consequence of the line emitting matter within the
innermost stable orbit being highly ionized, and is largely independent of the
parameters chosen for their model. If we restrict our attention to the 3-10 keV
band we may effectively remove this absorption edge by fitting a steeper power
law, but this results in a significant underprediction of the 0.4-0.5 keV flux.
We conclude that the data on MCG-6-30-15 are more consistent with the Kerr than
the Schwarzschild model.Comment: 5 pages with 5 postscript figures. Accepted for publication in MNRA
Construction of pseudo-bosons systems
In a recent paper we have considered an explicit model of a PT-symmetric
system based on a modification of the canonical commutation relation. We have
introduced the so-called {\em pseudo-bosons}, and the role of Riesz bases in
this context has been analyzed in detail. In this paper we consider a general
construction of pseudo-bosons based on an explicit {coordinate-representation},
extending what is usually done in ordinary supersymmetric quantum mechanics. We
also discuss an example arising from a linear modification of standard creation
and annihilation operators, and we analyze its connection with coherent states.Comment: In press in Journal of Mathematical Physic
An improved soft X-ray photoionization detector
Photoionization detector with an alumina shell, a beryllium foil window, and a xenon gas fill measures small incident photon fluxes from soft X rays. It has high spectral selectivity and quantum efficiencies, and a long shelf life. It minimizes electrical leakage and recontamination, and will hold a high vacuum
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